Yeah Bob that line you gave me does the same as N[Mean[Map[Last,
list]]]. It goes to the second part of the pair and takes the average
of all. I want to take only the average of the last half of the last
half. So i have 3000 pairs that look like {a,b}
i've got a way to take the means of all the b's in list of 3000. but i
want to take the mean's of the last 1500 b's.